The present invention relates to a cutting tool for chip removing machining, preferable milling, comprising at least one cutter, a holder holding the cutter, means for securing the cutter to the holder with a cutting edge of the cutter in a selectable cutting functional position in the direction of an intended axis of rotation of the holder as well as an arrangement for determining the position of the cutter with respect to the holder in the direction of said axis of rotation for enabling securing of the cutter through said means with the cutting edge in said selectable position, said arrangement comprising a body movably received in the holder and movable with surfaces to bear against the cutter for defining the position of the cutter in the direction of said axis of rotation as well as a screw which may be screwed in a threaded bore in the holder transversally to said axis of rotation and which has portions adapted to act upon said body in the direction of said axis of rotation upon screwing in said threaded bore, as well as an arrangement for determining the position of a cutter with respect to a holder in a cutting tool according to the preamble of the appended independent arrangement claim and a method for securing a cutter to a holder in a cutting tool according to the preamble of the appended method claim.
The invention relates to cutting tools for chip removing machining in general, such as for example turning or milling, but it is particularly interesting for machining in the form of milling, especially face milling, which is the reason for describing exactly this application hereinafter for illuminating, but accordingly not restricting the invention. In a cutting tool of the type defined in the introduction in the form of a face milling cutter one or more cutters may be arranged adjacent to a said arrangement for adjusting the position of a cutting edge on exactly these cutters. It is usually a question of cutters which have to project with the cutting edge thereof in the direction of said axis of rotation, i.e. in the cutting depth direction of the face milling cutter, longer than the corresponding cutting edge of the rest of the cutters of the cutting tool. It is important to be able to set or adjust the selectable cutting functional position of said cutting edge with a high accuracy so as to obtain an even surface in the face milling operation.
U.S. Pat. No. 5,391,023 describes a cutting tool of the type defined in the introduction. Said screw is in this cutting tool screwed into the holder thereof and displaces than a body, which in its turn displaces a cutter so that a cutting edge of the cutter arrives to a desired position. When the screw has been screwed in so far that the desired position of the cutting edge has been reached the screw has to be locked through a locking unit. When the locking of the screw and by that the body is carried out by means of the locking unit the setting of the cutter is influenced, so that there is a risk that it will differ from the desired position. Another drawback of this cutting tool and the arrangement thereof for determining the position of the cutter consists in that there is a play between said body and a bore in the holder receiving the body, which means that this play will during later machining be absorbed and change the position of the cutting edge.
It is desirable to provide a cutting tool of the type defined in the introduction for which said selectable position of the cutting edge of said cutter may be obtained with a higher accuracy than for such cutting tools already known.
According to an aspect of the present invention, a cutting tool is arranged with spring members adapted to act between the holder and said body for biasing the body against said portions of the screw.
This means that no locking unit is required, since the body of said arrangement will always be kept biased, i.e. under pretension, against said portions of the screw. Thus, the position of said body and by that the cutter will not be influenced by carrying out any locking of the body as for cutting tools of this type already known.
According to an embodiment of the invention said spring members are adapted to press said body oppositely to the screwing home direction of said screw in said threaded bore against said portions of the screw. This constitutes an advantageous and simple way of obtaining biasing of the body against screw portions for defining an exact position of the body and by that the cutter before this is secured with respect to the holder by said means.
According to another embodiment of the invention the cutter is so arranged in the holder with respect to said screw that the screw is adapted to influence the body to be displaced with said surfaces in the direction against said cutting edge upon screwing the screw in the unscrewing direction in said threaded bore so as to reach a position defining said selectable position of the cutting edge. It is totally contrary to cutting tools of this type already known to unscrew a screw in an arrangement of this type until the correct position has been reached of said body and by that the cutter influenced thereby, wherein in the cutting tools already known a screw is screwed in the screwing home direction for displacing a said body and by that the cutter to the desired position. This in combination with said biasing makes it very comfortable to carry out the adjustment of the cutter before it is secured to the holder.
According to another embodiment of the invention the holder is designed to hold the cutter with a surface directed towards said body and inclined with respect to a centre axis of said threaded bore for translating an axial movement of the screw when screwing into a movement of the body so that this comes closer to the cutter or displaces this in said intended rotation axis direction.
According to another embodiment of the invention said portion of the screw comprises a part of the lower side of a head of the screw, and the head of the screw may according to another embodiment of the invention be substantially conical, and said body has then a substantially conical part designed to provide said surface for bearing against said screw portions. A well defined very exact position of the body at a determined screwing depth of the screw is obtained by this conical shape in combination with said biasing.
According to another embodiment of the invention said body is sleeve-like with a through hole designed to receive the screw, and said screw portion is adapted to bear against said surfaces in the form of inner surfaces of the sleeve-like body. The holder has then advantageously a cavity, in the bottom of which said threaded bore is arranged, and this sleeve-like body is received in the cavity while being displaceable in the direction of said threaded bore.
According to another embodiment of the invention said spring members are formed by a compression spring, for example in the form of one or more cup springs, arranged to act between the bottom of said cavity and surfaces of the lower side of the sleeve-like body directed towards the cavity. Said biasing may by this be obtained through very simple means and with a higher accuracy.
According to another embodiment of the invention the location of the threaded bore in the cavity and the design of the sleeve-like body are so adapted to each other that the sleeve-like body is pressed tightly against a lateral wall of said cavity upon biasing action of said screw portions upon the body. Any play between said body and the bore in the holder and by that the holder is by this eliminated, so that at the same time the drawbacks mentioned above of such a play are eliminated and said selectable position of the cutting edge may be obtained with a very high accuracy.
More exactly, this may according to another embodiment of the invention be realized by the fact that the centre axis of said threaded bore is laterally displaced with respect to the centre axis of said cavity for pressing the sleeve-like body tightly against a lateral wall of said cavity on biasing action of said screw portions upon the body. Thus, a certain eccentricity is present between the cavity and the threaded bore for reliably eliminating said play.
According to another embodiment of the invention the cutting tool comprises a plurality of cutters distributed on the holder around said intended axis of rotation, and only some of said cutters of the cutting tool are arranged adjacent to a said arrangement for position determination. It is then preferred that the cutting tool is a face milling cutter. It is also within the scope of the invention to have a said arrangement adjacent to all cutters.
The invention also relates to an arrangement according to an aspect of the invention provided with spring members adapted to act between the holder and said body for biasing the body against said portions of the screw. The advantages of such an arrangement as well as an arrangement according to different embodiments of the invention as clearly as desired from the description above of the cutting tool according to the invention.
The invention also relates to a method for securing a cutter to a holder of a cutting tool of the type defined in the introduction, for a cutting tool which further has spring members adapted to act between the holder and said body for biasing the body against said portions of the screw, the screw is firstly screwed in the screwing home direction in the threaded bore, the screw is then screwed in the unscrewing direction in the threaded bore until the body influences said cutter in the direction of said intended axis of rotation to reach said selectable position, and then the cutter is then secured in this position. This constitutes a simple and comfortable way to obtain a precise securing of the cutter in a selectable position with respect to the holder of the cutting tool.
Further advantages as well as advantageous features of the invention appear from the description following.